258 Progress in Science. (April, 
Schuylkill, Northumberland, Columbia, and Dauphin, 129 fatal accidents 
occurred during the yéar, but it is notable that only s¢x of these deaths resulted 
from explosions of fire-damp. 
At arecent meeting of the Wigan Field Naturalists’ Society, Mr. Perrins 
read a paper on the probable duration of the important coal-field of Wigan. 
Coming from one of the leading mining surveyors of the town, Mr. Perrins’s 
estimate deserves attention. For the purpose of his enquiry he considers that 
the coal-field occupies an area embraced within a radius of two miles from the 
parish church. In this district there are about twelve workable coal-seams, 
and the author describes the geological features of each of these in succession. 
He divides the field into a number of belts, each of which is separately 
examined, and its yield of coal estimated. We pass over these details, how- 
ever, and arrive at once at the aggregate result. The whole of the Wigan 
coal-field originally contained an amount of mineral computed at 231,810,000 
tons. Of this quantity 96,285,000 tons have already been removed, thus 
leaving 135,525,000 tons still underground. At the present rate of working 
about 2,000,000 tons are removed annually; and assuming this rate to con- 
tinue, without increase or diminution, the Wigan coal-field will be exhausted 
in little more than fifty years. Seeing that these collieries employ, directly 
and indirectly, about 7a00 men, the gradual diminution of the coal must have 
a serious social influence upon the locality. It is cheering, however, to re- 
member that the iron trade around Wigan has of late received a great impetus, 
and it is therefore to be hoped that the development of this industry may 
compensate for the decline of the coal trade. 
A successful trial of Mr. G. L. Scott’s recently-patented steam-ventilator 
has been made at the Lower Moor Colliery, at Oldham, where a 4-feet seam 
of coal, faulted in all directions, is worked by intricate galleries extending for 
a distance of a mile from the shaft, the shaft being 888 feet in depth. A brick 
chamber, in communication with the upcast shaft, is covered by perforated 
iron plates carrying 72 vertical cast-iron pipes, each about 5 feet in length and 
7 inches in internal diameter. Inside each of these pipes is a small vertical 
steam pipe, which terminates by an orifice, ;3,ths of an inch in diameter, at 
about 2 feet below the top of the larger pipe. The system of pipes forms a 
rectangular arrangement occupying a space about so feet square, and is supplied 
with steam by a 4-inch pipe from the boilers of the winding and pumping en- 
gine. The results obtained by the use of this simple steam-ventilator compare 
favourably with those of the old furnace system, but it was not considered 
necessary, at the trial in question, to test the full power of the new apparatus. 
It is almost needless, however, to state that any ventilator which—like this 
steam apparatus—can be placed at the surface, so as to be under complete 
control, must possess great advantages over the ordinary system of ventilation, 
in which the apparatus is lodged in the pit itself. 
To prevent accidents from over-winding in mine-shafts, an ingenious appa- 
ratus has been patented by Mr. W. Walker. The load to be raised is carried 
by chains or ropes attached to the lower ends of two curved metal levers, 
hinzed together in the middle, and connected above with the winding-rope or 
chain. These levers are so constructed that when the load is being raised 
their lower ends diverge, whilst the upper extremities remain closed together, 
and hold the winding-rope between them. On the other hand, if the levers 
turn upon their common hinge, the lower parts are brought together, and the 
upper ends open out so as to release the rope, At that point which forms a 
limit to the raising of the load, and beyond which it would be dangerous to 
wind, there is a fixed beam, with an aperture sufficiently large to admit the 
winding-rope and the head of the safety apparatus. In the event of over- 
winding, the upper parts of the levers pass through this aperture, but the rest 
of the apparatus is arrested by a guard-plate, or collar, which is placed over 
the levers, and comes in contact with the under side of the beam. As the load 
now tends to rise, the distended ends of the levers are brought together by 
pressure against the sides of a slot in the collar, and as the lower ends of the 
levers come together, the upper parts forming the head fall apart, and rest upon 
